Electric incandescent lamp



No v. 3, 1942.

l. H. VAN HORN ELECTRIC INCANDESCENT LAMP Filed April 30, 1941 2 Sheets-Sheet 1 lnven'tor Irvin H. VanHorn,

His Attor'neg.

Nov. 3, 1942. 1. H. VAN HORN 2,300,997

ELECTRIC INCANDESCENT LAMP Filed April 30, 1941 4 2 Sheets-Sheet 2 Inven'kor: Irvin H. VanHorn,

His ATforne Patented Nov. 3,, 1942 ELECTRIC lNCANDESCENT LAMP Irving H. Van Horn, East Cleveland, Ohio, assignor to General Electric Company, a corporation of New York Application April 30, 1941, Serial No. 391,178

13 Claims.

My invention relates in general to electric incandescent lamps and more particularly to relatively high-wattage projection lamps such as are used for projection service. Still more particularly my invention relates to a double filament projection lamp and to a blackening control arrangement therefor.

Stereopticon projectors, have recently been introduced on the market lnwhich two separate and vertically spaced optical systems are utilized for the purpose or projectingtwo separate and more or less superimposed images on the screen to thereby impart to the projected pictures the illusion of depth. The source of illumination for such stereopticon projectors is conveniently constituted by a single electric incandescent lamp having two separate concentrated filaments of the monoplane or biplane type connected in parallel and mounted one above the other in a common enclosing bulb or envelope, the two filaments being so spaced and located relative to the lamp base as to be positioned in exact alignment with the two optical systems of th projector when the lamp is in place within its socket.

M Obviously, to obtain the best projection from such stereopticon projector arrangement, it is desirable that the illumination from each optical system be substantially of the same intensity.

illumination from the other light source or sources is to be collected. 7

Another object of my invention is to provide an elongated electric incandescent lamp having a plurality of separat and distinct light sources therein spaced apart longitudinally of the enclosing lamp envelope and in which the illumination provided by the lamp from each light I source is maintained at a substantially uniform However, where multiple filament lamps having no blackening control means are used, the illumination through the upper optical system of the projector decreases rather rapidly with lamp life due to the deposit of blackening from the lower lamp, filament which forms on that part of the lamp bulb wall above the lower filament including that portion of the bulb wall opposite the upper filament and in alignment with the upper- Such blackenoptical system of the projector. ing deposit materially obstructsvthe passage of the light rays from the upper filament after a' relatively-short period of lamp operation, with of the lamp.

One object of my invention is to provide a multiple filament electric incandescent lamp having means for preventing theblackening from one of the light sources from depositing on those portions of the envelope wallthrough which the value throughout the useful life of the lamp.

Still another object of my invention is to provide, in an elongated double filament electric incandescent lamp having a pair of separate and distinct filaments spaced apart longitudinally oi the :enclosing lamp envelope, blackening control means for preventing the blackening from one of said filaments from depositing on those portions of the lamp envelope laterally opposite the other of said filaments.

' A feature of the invention is the provision of suitable blackening collector or'control means intermediate the spaced filaments to thereby collect the blackening from one of said filaments and localize the deposit of the same onto those portions of the bulb wall immediately opposite the said blackening control means.

a Further objects and advantages of my invention will be apparentfrom the following description of species thereof and from the accompanying drawings'in-which:

Fig. 1 is a perspective view of an electric incandescent lamp comprising my invention, the

bulb of the lamp being shown partly in section; Fig. 2 is a similar view of a modification of my invention; Fig. 3 is a transverse section taken on the line 3+3 of Fig. 2; Fig. 4 is an elevation, partly in section, of another modification Of my invention; Fig. 5 is a perspective view of the lamp shown in Fig. 4, th bulb being shown partly in section; Fig. 6 is a perspective view similar to Fig. 5 of still another modification of my invention; Fig. '7 is a transverse section on the line l--l of Fig. 6.

Referring to the drawings, the lamp shown in Fig. 1 comprises an elongated, preferably cylindrical, sealed bulb or envelope III of glass or other suitable light-transmitting material having, at one end thereof, a neck portion ll provided with a re-entrant stem [2. The said stem I2 is provided with a press portion l3 into which a pair of relatively rigid leading-in wires (4, M are sealed, the said leading-in wires extending in any suitable manner, such as by the convenso as to provide transversely extending support arms I5, I5.

Mounted on the support arm portions I5, I of the leading-in wires I4 is a filament support framework comprising a pair of relatively rigid inner support leads or standards I6, I6 secured to the free ends of the support arms I5, as by welding, and extending in a direction parallel to the longitudinal axis of the bulb to a point adjacent the tip of the bulb. The said support leads or standards I6 are held in rigid spaced relationship by a plurality of bridge or tie members comprising an upper tie member I I bridging the uppermost ends of the inner support leads, a spaced pair of tie members I8, I9 bridging the inner leads at points adiacenttheir midpoints, and a lower tie member bridging the lowermost ends of the inner support leads. Each of said bridge members II, I8, I9 and 20 comprises an insulating member 2|, preferably consisting of a short length of glass rod, and a pair of relatively rigid tie wires 22 spot-welded or otherwise secured at one end to the inner support leads I6 and embedded in, or otherwise secured at their other ends to the insulating member 2I.

Mounted within the bulb between the inner support leads I6 are a pair of vertically spaced tungsten filaments comprising an upper filament 23 disposed between the upper pair of bridge members I1, I8, and a lower filament 24 disposed between the lower pair of bridge members I9, 20. The filaments 23, 24 illustrated are of the socalled monoplane type comprising a plurality of vertically extending parallel coiled segments joined by upper and lower uncoiled or bight portions 25 and 26 respectively, the coiled segments being located in a common plane substantially coinciding with the plane of the inner support leads I 6, I6. The filaments 23, 24 are supported at the top by support wires 21 having hooked lower ends engaging the upper bights 25 and secured at their upper ends to the insulating member 2| of the respective upper bridge or tie members I1 and I 9. The filaments are similarly supported at the bottom by anchor wires 28 having open hooks at their upper ends engaging the lower bights 28 and secured at their lower ends to the insulating members 2I of the respective lower bridge or tie members I8 and 20. The said support wires 21 and anchor wires 23 are preferably embedded in the glass insulating members 2I. Th filaments 23, 24 are formed with coiled end segments 29 extending, transversely of the bulb axis in opposite directions and welded or otherwise electrically connected to the inner support leads IS, It to thereby form the electrical connection between the filaments and the leading-in wires I4.

Thefilaments 23 and 24 are positioned within the bulb in definite predetermined relation with respect to .one another (i. 'e., they are spaced apart a predetermined distance along the longitudinal axis of the bulb) as well as with respect to the base I5 so that when the lamp is screwed or otherwise inserted in the lamp socket of the stereopticon projector, the filaments will be in exact optical alignment with the corresponding optical systems of the projector.

In accordance with the invention, the deposition of the blackening from the lower filament 24 on those portions of the bulb wall laterally opposite the upper filament 23, and resultant premature termination of the useful life of the lamp, is prevented by the use of suitable blackening collector and control means or shield means comprising a relatively thin refractory disc 30 of ceramic or other suitable material arranged transversely, within the lamp bulb I0 intermediate the two filament 23, 24. Thesaid disc 30 is of a diameter sufilcient to close off or extend across a substantial proportion of the cross-sectional area of the bulb, and is preferably made of a ceramic material commercially known as Alsimag"; but it may be made of any other ceramic possessing fair strength and characterized by freedom from moisture, such as porcelain, lava or silimanite. Alsimag" is useful for the reason that it will withstand relatively high temperatures without giving up harmful impurities.

The ceramic disc 30 is disposed concentrically within the lamp bulb In between the two central bridge or tie members I8, I9, and is supported in place by laterally extending bent portions or loops 3| formed in the inner support leads It, It. The arms of the loops or bent portions 3i tightly clamp the ceramic disc 30 therebetween, so as to provide a firm support for the disc. Suitable openings 32 are provided in the ceramic disc through which extend those portions of the inner support leads I6 which Join the arms of the bent or loop portions 3|.

During the operation of the lamp shown in Fig, 1, the particles of tungsten which vaporize oil the lower filament 24 are carried upwards by the convection currents within the lamp bulb where they deposit partly on the under surface of the ceramic disc 30 and partly on those portions of the bulb wall immediately below and adjacent the periphery of the ceramic disc. The deposition of the filament particles on such portions of the bulb wall results from the baflie action of the ceramic disc 30, the disc deflecting the rising convection currents laterally outwards towards those portions of the bulb wall immediately below and adjacent the periphery of the disc where the filament particles carried by uch deflected convection currents are deposited. Thus, the ceramic disc 30 functions as a blackening collector and control means serving to localize the blackening deposit from the lower filament 24 on those portions of the bulb wall intermediate the two filaments 23, 24 and out of lateral alignment therewith. Inasmuch as the blackening from the upper filament 23 deposits on the tip of the bulb II! where it does not interfere in any way with the lateral projection of light from either the upper or the lower filaments 23, 24, it will be evident that the construction according to the invention provides an eflicient two-filament projection lamp wherein the formation of a blackening deposit on those portions of the bulb wall laterally opposite the upper filament 23 where it would materially diminish the illumination therethrough after a relatively short period of lamp life, as well as laterally opposite the lower filament 24, is effectively prevented.

In the modification shown in Figs. 2 and 3, the lamp construction there illustrated is very much the same as that shown in Fig. 1 except for the blackening collector and control means which in this form of the invention comprises a. discshaped member composed of a pair of fiat semicircular members 33 of perforate material, preferably of wire screen, mounted transversely within the lamp bulb so as to form, in eflect, a wire screen disc disposed across the cross-sectional space within the lamp bulb l8. Each semi-circular screen member 33 is supported by a pair of relatively rigid support wires 34 secured to the screen member in any suitable manner and embedded at their inner ends in the insulating member 2| of a central tie member 35.- The screen support wires 34 may be soldered or welded to the wire screen members 33, or they may be simply threaded through the mesh openings therein. The lower ends of the anchor wires 28 for the upper filament 23, and the upper ends of the support wires 21 for the lower filament 24, are embedded in the insulating member 2| of the center tie member 35 so that the latter serves as a common support means for both the upper and lower filaments 23, 24. To prevent the wire screen members 33 from touching the inner lead wires I6 or the tie wires 22 of the central tie member 35 so as to possibly result in a short circuit across the said inner lead wires I5, the wire screen members 33 are cut away or recessed at each side of the insulating member 2|, as indicated at 3B in Fig. 3. To'further rigidify the lamp mount structure and prevent the same from moving transversely of the plane of the filaments 23, 24 and inner leads IS, a pair of laterally extending guide or positioning wires 31 are provided at the top of the mount structure which are secured at their inner ends to the insulatin member 2| of the upper bridge member l1 and extend laterally out therefrom, at right angles to the said plane of the filaments 23, 24 and inner leads l5, into engagement with the wall of the bulb l8.

The wire screens 33 diffuse or break up the hot gas convection currents rising from the heated-lower filament 24 with the result-that some of the blackening particles carried by such hot gas currents are effectively collected on the wire screens 33 while the remainder are deposited on the bulb wall immediately adjacent the wire screens. Thus, that portion of the blackening from thelower filament which actually deposits on the bulb wall, is localized to an area immediately contiguous the wire screens 33 and outof lateral alignment with the upper filament 23, so that it does not interfere in any way with the lateral transmission of light from the upper filament out through the lamp bulb.

While the constructions shown in Figs. 1-3 are entirely satisfactory for projection lamps of the lower wattages, i. e., up to 600 watts or thereabouts, I have found that to effectively control the blackening deposit in higher wattage projection lamps of the order of 750 watts and above, it is necessary to employ blackening control arrangements such as shown in Figs. 4-7.

Referring to the form of the invention shown. in Figs. 4-5, the lamp there shown is of substantially the same construction as that shown in r Fig. 1 except that it is provided with additional embedded at one end in the glass insulating rods 2| oi the bridge members l1 and I3 above each filament 23, 24. The said wires 48 extend laterally out from the said glass rods to the wire screen members 33, 38 to which they are secured in any suitable manner, such as by clamping the wire screens within hooks 4| formed at the outer ends of the support wires".

The lower screen 38 provides additional means for collecting the blackening from the lower filament 24 and, by reason of its diffusing action on the hot gas convection currents rising from the lower filament 24, causes such hot gas currents to be directed towards and against a greater area of the bulb wall between the upper extremity of the lower filament and the ceramic disc 38 than is the case where the ceramic disc 38 alone is used, whereby greater opportunity is afforded for the blackening particles carried by such convection currents to deposit on the bulb wall below the ceramic disc 30. The upper screen 38 performs in the same way as the lower screen 39,

such screen serving to collect a part of the blackening from the upper filament 23 and to diffuse and direct the hot gas convection currents rising from the upper filament laterally outwards towards the bulb wall so as to minimize the de posit on the upper portions of the bulb wall by distributing the blackening over a greater area of the bulb wall above the upper filament 23. It thus will be evident that the use of the additional screen members 38, 33 compensates for the increased amount of blackening which occurs in the higher-wattage lamps and effectively prevents the depositionof any noticeable amount of blackening on those portions of the bulb wall laterally opposite the filaments 23, 24.

In the modification shown in Figs. 6-7, the lamp construction is substantially the same as that shown in Fig. 2, except for the blackenin control means which in this case comprises an upper trough-shaped wire screen member 38 the same as in Figs. 4-5, and a pair of lower wire screen members 42, 42 each consisting of a transversely arranged flat semi-circularly shaped portion 43, similar to the wire screen members 33 in Figs. 2-3, and a downwardly projecting arouate portion 44 depending from the periphery of the fiat semi-circular portion 43 and conforming substantially to the circular cross-section of the,

bulb. The screen members 42 are mounted at a point intermediate the two filaments 23, 24 and out of lateral alignment therewith, and are so supported relative to one another as to form, in effect, an inverted cup having cylindrical sides concentric with the cylindrical bulb wall. The wire screens 42 are supported in place in the same way as the wire screens 33 in Figs. 2-3, that is, by laterally extending support wires 34 embedded at their inner ends in the glass insulating rod 2| of the central bridge member 35 and suitably secured to the fiat semi-circular portions 43 of the screens. Likewise, as with the screens 33 in Figs. 2-3, the edges 45 of the wire screens 42 are spaced a suflicient distance from the inner leads I6 and the tie wires 22 to prevent the screens from touching such leads or tie wires and so producing a short circuit between the inner leads I6.

In the appended claims, the expression planar filaments is intended to cover a, filament of the character exemplified by a monoplane or biplane type filament, as hereinbefore described.

What I claim as new and desire to secure by letters Patent of the United States is:

1. A gas-filled electric incandescent lamp comprising a light-transmitting bulb, a pair of spaced filaments mounted within said bulb above one another, and blackening control means disposed within said bulb between said filaments for preventing the blackening particles from the lower filament from depositing on that portion of the bulb wall laterally opposite the upper filament.

2. An electric incandescent lamp comprising a tubular light-transmitting bulb, a pair of filaments mounted within said bulb in spaced relation longitudinally of said bulb so as to be disposed one above the other, blackening control means disposed within said bulb between said filaments for localizing the blackening of the bulb from the lower filament to a portion of the bulb wall intermediate the said filaments and out of lateral alignment therewith, and other blackening control means disposed within said bulb directly above the upper filament for collecting, and distributing on the upper portion of the bulb wall, the blackening from the upper filament.

3. An electric incandescent lamp comprising a tubular light-transmitting bulb, a pair of filaments mounted within said bulb in spaced relation longitudinally of said bulb so as to be disposed one above the other, and a pair of perforate members disposed within said bulb one intermediate said filaments for localizing the blackening of the bulb from the lower filament to a portion of the bulb wall intermediate the said filaments and out of lateral alignment therewith and the other disposed above the upper filament for collecting and distributing on the upper portion of the bulb wall the blackening from the upper filament, said perforate members extending across a substantial proportion of the. cross-sectional area of said bulb. I

a. An electric incandescentlamp comprising a tubular light-transmitting bulb, a pair of filaments mounted within said bulb in spaced relation longitudinally of said bulb so as to be disposed one above the other, blackening control means disposed within said bulb between said filaments and out of lateral alignment therewith, said blackening control means comprising a transversely arranged refractory disc disposed concentrically within said bulb and extending across a substantial proportion of the cross-sectional area of said bulb and a perforate member disposed directly above the lower filament and beneath said refractory disc, said perforate member extending across a substantial proportion of the cross-sectional area of said bulb, and other blackening control means disposed directly above the upper filament and comprising a perforate member extending across a substantial proportion of the cross-sectional area of said bulb.

5. An electric incandescent lamp comprising a tubular light-transmitting bulb, a pair of planar filaments mounted within said bulb in spaced relation longitudinally of said bulb so as to be disposed one above the other with the plane of said filaments parallel to the longitudinal axis of said bulb, a transversely arranged refractory disc disposed concentrically within said bulbbetween said filaments and extending across a substantial proportion of the cross-sectional area of said bulb and an inverted trough-shaped wire screen disposed directly above the lower filament but beneath said refractory disc and arranged with its length parallel to the plane of said lower filament, and a second inverted trough-shaped wire screen disposed directly above the upper filament with its length parallel to the plane of said upper filament.

6. An electric incandescent lamp comprising a tubular light-transmitting bulb, a pair of planar filaments mounted within said bulb in spaced relation longitudinally of said bulb so as to be disposed one above the other with the plane of said filaments parallel to the longitudinal axis of said bulb, an inverted cup-shaped wire screen member disposed concentrically within said bulb between said filaments and extending across a substantial proportion of the cross-sectional area of said bulb, and an inverted trough-shaped wire, screen member disposed directly above the upper filament with its length parallel to the plane of said upper filament.

7. A gas-filled electric incandescent lamp comprising a tubular light-transmitting bulb which in the normal use of said lamp is arranged with its longitudinal axis vertical, a plurality of high wattage filaments in said bulb spaced longitudinally thereof so as to be disposed one above the other, and blackening control means disposed within said bulb for breaking up convection currents rising from the lower filament and preventing the blackening from one of said filaments from depositing on a portion of the bulb wall laterally opposite another of said filaments.

8. A gas-filled electric incandescent lamp comprising a tubular light-transmitting bulb which in the normal use of. said lamp is arranged with its longitudinal axis vertical, 2. pair of high wattage filaments in said bulb spaced longitudinally thereof so as to be disposed one above the other, and blackening control means disposed within said bulb between said filaments for breaking up convection currents rising from the lower filament and preventing the blackening particles from the lower filament from depositing on that portion of .the bulb wall laterally opposite the upper filament.

9. A gas-filled electric incandescent lamp comprising a tubular light-transmitting bulb which in the normal use of said lamp is arranged with its longitudinal axis vertical, a pair of high wattage filaments in said bulb spaced longitudinally thereof so as to be disposed one above the other. said filaments being permanently connected for simultaneous energization, and blackening control means disposed within said bulb between said filaments for breaking up convection currents rising from the lower filament and preventing the blackening particles from the lower filament from depositing on that portion of the bulb wall laterally opposite the upper filament.

10. A gas-filled electric incandescent lamp comprising a tubular light-transmitting bulb which in the normal use of said lamp is arranged with its longitudinal axis vertical, a pair of high wattage filaments in said bulb spaced longitudinally thereof so as to be disposed one above the other, and shield means disposed within said bulb between said filaments and in the path of the rising convection currents from the lower of said filaments for breaking up the said convection currents and directing them and the blackening. particles carried thereby against a portion of the bulb wall intermediate the said' filaments and out of lateral alignment therewith to thereby localize the blackening of the bulb from the11 lower filament to the said portion of the bulb wa 11. A gas-filled electric incandescent lamp comprising a tubular light-transmitting bulb which in the normal use of said lamp is arranged with its longitudinal axis vertical, a pair of high wattage filaments in said bulb spaced longitudinally thereof so as to be disposed one above the other, and a transversely arranged refractory disc disposed concentrically within said bulb intermediate said filaments and extending across substantially the entire cross-sectional area of said bulb but permitting gaseous intercommunication between the upper and lower portions of the bulb and serving to break up convection currents rising from the lower filament to prevent the blackening particles from the lower filament from depositing on the portion of the bulb wall laterally opposite the upper filament.

12. A gas-filled electric incandescent lamp comprising a tubular light-transmitting bulb which in the normal use of said lamp is arranged with its longitudinal axis vertical, a pair oi high wattage filaments in said bulb spaced longitudinally thereof so as to be disposed one above the other, and a blackening control wire screen member disposed within said bulb intermediate said filaments to break up convection currents rising from the lower filament and prevent the blackening particles from the lower filament from depositing on the bulb wall opposite the upper filament.

13. A gas-filled electric incandescent lamp comprising a tubular light-transmitting fbulb which in the normal use of said lamp is arranged with its longitudinal axis vertical, a pair of high wattage filaments in said bulb spaced longitudinally thereof so as to be disposed one above the other, and a blackening control member comprising, at least in part, a transversely arranged disc-shaped wire screen disposed concentrically within said bulb intermediate said filaments and extending across substantially the entire crosssectional area of said bulb and serving to break up convection currents rising from the lower filament to prevent the blackening particles from the lower filament from depositing on the portion of the bulb wall laterally opposite the upper filament.

IRVING H. VAN HORN. 

